Processes for forming polymeric seamless belts and imaging members

ABSTRACT

A process which includes providing a preform including a polymeric material formed to permit the introduction of a fluid under pressure into the preform, heating the preform to a temperature at or above the glass transition temperature of the polymeric material and below the melting temperature of the polymeric material, placing the heated preform into a substantially cylinderical mold with a polished seamless inside surface, introducing a fluid under pressure into the heated preform while maintaining the preform axially centered in the mold, thereby causing the preform to expand without contacting the mold surface, subsequently causing the preform to expand until it contacts the mold surface, heating the expanded preform to an appropriate heat setting temperature above the stretching temperature and below the melting temperature of the polymeric material while maintaining fluid pressure, and subsequently cooling the set preform, resulting in formation of a biaxially oriented seamless belt. The thin walled, high surface quality biaxially oriented seamless belt thus formed is then either used as a substrate for an electrophotographic or ionographic imaging member or used as a paper handling belt in the document handler of an electrophotographic copier.

BACKGROUND OF THE INVENTION

The present invention is directed to a process for forming polymericseamless belts. More specifically, the present invention is directed toa process for forming biaxially oriented polymeric seamless or endlessbelts by a stretch blow molding process followed by heat setting andcooling of the resulting belt. One embodiment of the present inventionis directed to a process which comprises providing a preform comprisinga polymeric material, heating the preform to an appropriate stretchingtemperature at or above the glass transition temperature of thepolymeric material and below the melting temperature of the polymericmaterial, placing the heated preform into a substantially cylindricalmold with a polished seamless inside surface, introducing a fluid underpressure into the heated preform while maintaining the preform axiallycentered in the mold, thereby causing the preform to expand both axiallyand radially without contacting the mold surface, subsequently causingthe preform to expand until it contacts the mold surface, heating theexpanded preform to an appropriate heat setting temperature above thestretching temperature and below the melting temperature of thepolymeric material while maintaining fluid pressure, and subsequentlycooling the set preform. Another embodiment of the present invention isdirected to a process for preparing an electrophotographic imagingmember which comprises preparing a seamless belt by the process of thepresent invention as detailed herein and coating onto the seamless belta layer of a photogenerating material. Yet another embodiment of thepresent invention is directed to a process for preparing a dielectricreceiver suitable as an imaging member for ionographic imagingprocesses.

Imaging members for electrophotographic imaging systems comprisingselenium alloys vacuum deposited on rigid aluminum substrates are known.These imaging members require elaborate, highly sophisticated, andexpensive equipment for fabrication. Imaging members have also beenprepared by coating rigid substrates with photoconductive particlesdispersed in an organic film forming binder. Coating of rigid drumsubstrates has been effected by various techniques such as spraying, dipcoating, vacuum evaporation, and the like. Rigid drum imaging members,however, limit apparatus design flexibility, are less desirable forflash exposure, and are expensive. Flexible organic imaging members aremanufactured by coating a web and thereafter shearing the web intosegments which are then formed into belts by welding opposite ends ofthe sheared web. The resulting welded seam on the imaging member,however, disrupts the continuity of the outer surface of the imagingmember and must be indexed so that it does not print out during animaging cycle. Efficient stream feeding of paper and throughput are thusadversely affected because of the necessity to detect a seam within thelength of each sheet of paper. The mechanical and optical devicesrequired for indexing add to the complexity and the cost of copiers,duplicators, and printers, and reduce the flexibility of design. Weldedbelts are also less desirable for electrophotographic imaging systemsbecause the seam forms a weak point in the belt and collects toner andpaper debris during cleaning, particularly with wiper blade cleaningdevices. Accordingly, seamless belts suitable as substrates forelectrophotographic or ionographic imaging members are particularlydesirable.

In addition, seamless belts for use in document handling systems inprinting, copying, and duplicating apparatuses are particularlydesirable. Document handler belts with seams tend to accumulate dirt inthe seam area, thus necessitating frequent cleaning. When the documenthandler belts are in high volume copiers or duplicators generating over100 copies per minute, it may be necessary to clean the document handlerbelt seams frequently. In addition, the seam of a document handler beltcan provide a weak point with respect to belt breakage. Thus, a seamlessdocument handler belt is desirable to reduce dirt build up on the beltand to reduce belt breakage.

Processes for forming biaxially oriented products by blow moldingprocesses are known. For example, Soviet Union Inventor's Certificate716,848 discloses a method for making drive belts from plasticbasedmaterials by molding blanks from granules of polyethyleneterephthalateand blowing the blank in a mold so that the material is subject tobiaxial orientation in mutually perpendicular directions, followed bythermally fixing the belt in a liquid-heat-carrier medium and cuttingthe tubular blank. According to this reference, the quality of thearticle is increased, on account of stabilizing the coefficient oforientation of the blank along its length, by carrying out the blowingwhile additionally limiting its size from below by using a bottomattachment to regulate the height. Additionally, Sovient UnionInventor's Certificate No. 305,074 discloses a method for themanufacture of drive belts which comprises molding a workpiece frompolyethylene terephthalate resin granules, placing the workpiece in amold, placing the mold containing the workpiece into a liquid heatcarrier, introducing an inert gaseous heat carrier under pressure intothe inner cavity of the workpiece heated to a state of softness toinflate the workpiece to the dimensions of the mold, and thermallyfixing the inflated workpiece in the liquid heat carrier medium. Thecylindrical portion of the inflated balloon is then cut into rings ofrequired width.

In addition, U.S. Pat. No. 2,335,978 (Vogt), the disclosure of which istotally incorporated herein by reference, discloses a method of makingcontainers such as flexible bags and liners for cartons. The methodentails applying localized heat to the exterior surfaces of the wallportions of a container consisting of a flexible, thermoplastic sheetmaterial which, when heated and rendered plastic, may be stretchedlengthwise of the container and expanded circumferentially to increaseits superficial area and which when again cooled will to a large degreeretain its expanded condition. Application of heat softens the walls ofthe container, and a fluid pressure is subsequently applied within thecontainer and a force is applied lengthwise to expand and lengthen thewalls and increase their superficial area. Subsequently, the containeris cooled in its expanded condition.

Further, U.S. Pat. No. 3,910,743 (Farrell), the disclosure of which istotally incorporated herein by reference, discloses an injection blowmolding process wherein a semi-liquid and molten plastic is injectedinto a cavity into which a core rod extends. The molten plastic isdischarged into the mold cavity and the material spreads in alldirections around the core rod to fill the cavity and form a parisonaround the core rod. The core rod can be covered with an elastomermaterial which forms a balloon that hugs the core rod when the balloonis deflated. After a parison has been applied over the core rod, thecore rod is withdrawn from the injection mold. Subsequently, the parisonis blown by blowing into the parison or the balloon. According to theteachings of this patent, the plastic is injected into the cavity of theinjection mold at the neck end of the core rod, and the application ofthe plastic to the surface of the core rod is then controlled by havinga tube which surrounds the core rod and which fills most of theinjection mold cavity. As the plastic material enters the mold cavity,the tube is withdrawn and the plastic material contacts the end face ofthe tube and advances as the tube withdraws so as to apply the plasticmaterial to the core rod as a wave of plastic which rolls down thelength of the core rod as the tube withdraws. U.S. Pat. No. 3,936,260(Farrell), the disclosure of which is totally incorporated herein byreference, also discloses an injection blow molding process wherein thelength to diameter ratio of plastic articles made on injection moldingmachines is increased without using long and relatively thin core rods.The first part of the blowing operation stretches the parison lengthwisebefore there is any substantial displacement of the parison in a radialdirection. At the start of the blowing operation, a tube surrounds andconfines radial expansion of the parison, but the tube is withdrawnprogressively as the blowing operation continues. U.S. Pat. No.4,363,619 (Farrell), the disclosure of which is totally incorporatedherein by reference, discloses an apparatus and method for making a widemouth container by an injection blow molding process whereinsubstantially the entire container is multiaxially oriented in itsformation.

Additionally, European Patent Document 12, 481 (Neundorf et al.)discloses a hollow molding manufacturing process from partiallycrystalline polypropylene or ethylene-propylene copolymers. The processis carried out in one stage in the presence of benzoic acid, and entailscooling the parison to a temperature 10° to 60° C. below the meltingrange of the polymer and then reheating to the usual stretchingtemperature of 1° to 20° C. below the melting range and molding to ahollow body by biaxial stretching.

In addition, British Patent 2,089,276 (Reed et al.), U.S. Pat. No.4,447,199 (Reed et al.), and U.S. Pat. No. 4,547,416 (Reed et al.), thedisclosures of each of which are totally incorporated herein byreference, disclose a process for making biaxially oriented tubulararticles which will provide bodies for processable food containers. Thearticles are made from an elongate tube of thermoplastic material as itemerges from an extruder. The process entails repeatedly performing acycle which comprises engaging the tube by a first clamping means over afirst region at a leading end of the tube and by a second clamping meansover a second region at a spacing from the first region, so as to definebetween clamping regions a portion of the tube to be longitudinallystretched and radially expanded; moving the clamping means apart tostretch the tube portion longitudinally and admitting pressure fluid tothe tube portion to expand it radially and form a bubble of biaxiallyoriented thermoplastic material adjacent to the leading end of the tube;and severing at least a substantial portion of the bubble from the tubeto form the tube with a new end as the leading end of the tube for thesucceeding cycle. U.S. Pat. No. 4,735,538 (Reed et al.) discloses aprocess of forming biaxially oriented tubular articles by repeating acycle which comprises engaging a thermoplastic tube by a first clampingmember over a first region at a trailing end of the tube and engagingthe tube by a second clamping mechanism over a second region at aspacing from the first region so as to define between the clampingmechanisms a portion of the tube to be longitudinally stretched andradially expanded; admitting pressure fluid into the tube portion toexpand it radially and form a biaxially oriented bubble adjacent to theleading end of the tube; and severing a substantial part, but not all,of the bubble from the tube to form the tube with a radially outwardlyflared end as the leading end of the tube for the succeeding cycle.

Further, U.S. Pat. No. 4,499,045 (Obsomer), the disclosure of which istotally incorporated herein by reference, discloses a process for theproduction of tubes of a molecularly oriented plastic which comprisesheating a plastic tube to a temperature at which stretching induces amolecular orientation and clamping a portion of the tube in a sleeve,followed by introducing a fluid under pressure into the portion of tubeand moving the sleeve along the portion of the tube to cause itsprogressive radial expansion until it makes contact with a mold.

Additionally, U.S. Pat. No. 4,632,656 (Eyeglaar et al.) discloses anapparatus for manufacturing molecularly oriented plastic pipes. Theapparatus includes a tubular mold of transverse dimensions equal tothose of the pipe to be produced and equipped with a device foradmitting a fluid under pressure into a region intended to receive thepipe section to be expanded. The apparatus also includes a member forclosing and grasping one end of the pipe section of a tubular sleevewhich opens into the mold by an end away from the closing and graspingmember, the transverse dimensions of which correspond to those of thepipe section, and a means for causing a controlled relative axialdisplacement of the sleeve in relation to the closing and graspingmember in which the open end of the sleeved is equipped with an annularplunger incorporating a surface of a frustoconical shape extendingtoward the inner wall of the mold and widened out in a direction awayfrom the closing and grasping member. The apparatus produces pipesections oriented in a reproducible manner and especially suitable forthe construction of pipelines for fluids under pressure.

In addition, U.S. Pat. No. 3,733,309 (Wyeth et al.), the disclosure ofwhich is totally incorporated herein by reference, discloses a hollow,biaxially oriented thermoplastic article, particularly a bottle,prepared from polyethylene terephthalate wherein the article has aninherent viscosity of at least 0.55, a density of about 1.331 to 1.402,and a ratio of article weight in grams to volume in cubic centimeters ofabout 0.2 to 0.005:1. If desired, the article thus formed can be heatset to achieve a uniform crystallinity in each article.

Also of interest are the following references: "Biaxially OrientedPolyethylene Terephthalate Bottles: Effects of Resin Molecular Weight onParison Stretching Behavior," C. Bonnebat et al., SPE ANTEC TechnicalPapers, vol. 25, page 273 (1979); "Biaxially Oriented Poly(EthyleneTerephthalate) Bottles: Effects of Resin Molecular Weight on ParisonStretching Behavior," C. Bonnebat et al., Polym. Eng. Sci., vol. 21, no.4, page 189 (1981); "Blowing of Oriented PET Bottles: Predictions ofFree Blown Size and Shape," L. Erwin et al., Polym. Eng. Sci., vol. 23,page 826 (1983); "Stretch Blow Molding," S. L. Belcher, Modern PlasticsEncyclopedia, vol. 64, page 206 (1987); "A Survey of Film ProcessingIllustrated With Poly(Ethylene Terephthalate)", Polym. Eng. Sci., vol.18, no. 15, page 1163 (1978); D. V. Rosato and D. V. Rosato (Eds.), BlowMolding Handbook (1989); and "Meet `COFO`, a New Way to Make Multi-layerParts," O. G. Raspor and J. Eichhorn, Plastics World, Feb. 1988, page44. The disclosures of each of these references are totally incorporatedherein by reference.

Although known molding processes are suitable for their intendedpurposes, a need remains for processes for preparing seamless beltssuitable for electrophotographic and ionographic applications. Inaddition, a need continues to remain for processes for preparingseamless belts with excellent tensile strength. A need also exists forprocesses for preparing seamless belts with excellent thicknesstolerances. Further, there is a need for processes for preparingseamless belts with multi-layer structures and excellent thicknesstolerances for the layers. There is also a need for processes forpreparing seamless belts with excellent surface uniformity.Additionally, a need exists for processes for preparing seamless beltsthat do not undergo any substantial degree of deformation upon beingheated. Further, there is a need for processes for preparing seamlessbelts that are substantially transparent and exhibit little or no hazingas a result of the belt formation process. In addition, there is a needfor stretch blow molding processes that enable preparation of seamlessbelts with a thickness of less than 0.010 inch, and frequently as low as0.001 inch. A need also remains for processes for preparing seamlessbelts that are suitable as photoreceptor substrates and as documenthandler belts that exhibit reliability and require less frequentcleaning, thereby reducing costs. There is also a need for processes forpreparing seamless belts with high surface quality in that the surfacesare smooth and free of defects.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a process forpreparing seamless belts suitable for electrophotographic andionographic applications.

It is another object of the present invention to provide a process forpreparing seamless belts with excellent tensile strength.

It is yet another object of the present invention to provide a processfor preparing seamless belts with excellent thickness tolerances.

It is still another object of the present invention to provide a processfor preparing seamless belts with multi-layer structures and excellentthickness tolerances for the layers.

Another object of the present invention is to provide a process forpreparing seamless belts with excellent surface uniformity.

Yet another object of the present invention is to provide a process forpreparing seamless belts that do not undergo any substantial degree ofdeformation upon being heated.

Still another object of the present invention is to provide a processfor preparing seamless belts that are substantially transparent andexhibit little or no hazing as a result of the belt formation process.

It is another object of the present invention to provide stretch blowmolding processes that enable preparation of seamless belts with athickness of less than 0.010 inch, and frequently as low as 0.001 inch.

It is yet another object of the present invention to provide processesfor preparing seamless belts that are suitable as photoreceptorsubstrates and as document handler belts that exhibit reliability andrequire less frequent cleaning, thereby reducing costs.

It is still another object of the present invention to provide processesfor preparing seamless belts with high surface quality in that thesurfaces are smooth and free of defects.

These and other objects of the present invention (or specificembodiments thereof) can be achieved by providing a process whichcomprises providing a preform comprising a polymeric material, heatingthe preform to an appropriate stretching temperature at or above theglass transition temperature of the polymeric material and below themelting temperature of the polymeric material, placing the heatedpreform into a substantially cylindrical mold with a polished seamlessinside surface, introducing a fluid under pressure into the heatedpreform while maintaining the preform axially centered in the mold,thereby causing the preform to expand both axially and radially withoutcontacting the mold surface, subsequently causing the preform to expanduntil it contacts the mold surface, heating the expanded preform to anappropriate heat setting temperature above the stretching temperatureand below the melting temperature of the polymeric material whilemaintaining fluid pressure, and subsequently cooling the set preform.Alternatively, instead of stretching the preform both axially andradially by pressure from the fluid, the preform can be first stretchedmechanically in the axial direction by any appropriate means, such as astretching pin or the like, followed by stretching the preform radiallyby fluid pressure. Subsequently, the resulting film can be removed fromthe mold and cut to produce a belt of the desired width.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A, 1B, 1C and 1D illustrate schematically four preforms suitablefor the process of the present invention.

FIGS. 2A and 2B illustrate schematically two mold configurationssuitable for the process of the present invention.

FIGS. 3A, 3B, 3C, and 3D illustrate schematically the various stagesfollowing introduction of fluid into a heated preform as the preform issituated in a seamless cylindrical mold to cause expansion to thepreform's natural draw diameter according to the process of the presentinvention.

FIG. 4 illustrates an alternative embodiment of the present inventionwherein the preform is first stretched mechanically in the axialdirection and then stretched in the radial direction by introduction ofa fluid into the preform.

DETAILED DESCRIPTION OF THE INVENTION

The process of the present invention entails the formation of a seamlessendless belt by expanding a preform in a seamless mold by theintroduction into the preform of a fluid under pressure. The preform cancomprise any material desired for the final belt product. For example,when the seamless belt prepared according to this process is intendedfor use as an imaging member substrate or for use as a belt in adocument handler on a copier or duplicator, the desired material can beany polymeric material suitable for this function and suitable for theprocess of the present invention. Examples of suitable materials includepolyethylene terephthalate (PET), polypropylene, polyvinyl chloride(PVC), polystyrene, polyacrylonitrile and polyacetals, as well as otherorientable polymers such as polyamides, polyether ether ketone (PEEK),polyesters other than PET, and the like, as well as mixtures thereof.

In addition, various fillers can be included in the polymeric materialof the preform. For example, when a conductive belt is desired for useas an imaging member layer, the polymeric material can contain anysuitable conductive material, such as conductive carbon black, carbonfibers, stainless steel fibers, magnetite, nickel, graphite fiberscoated with a conductive material such as nickel, glass fibers coatedwith a conductive material, electroconductive tin oxide powders, or thelike, as well as mixtures thereof, in any effective or desired amount.Conductive belts are prepared according to the process of the presentinvention wherein the conductive filler is present in any effectiveamount, typically from about 2 to about 30 percent by weight, andpreferably from about 10 to about 15 percent by weight, although theamount can be outside of this range. Fillers can also be employed forother purposes, such as to impart color to the belt, structuralreinforcement, reduced triboelectric charging, or the like. Examples offiller suitable for these purposes include pigments such as titaniumdioxide (TiO₂), barium sulfate (BaSO₄), mixtures of TiO₂ and BaSO₄, andthe like as a whitener, glass fibers as reinforcement, antistatic agentsfor reduced triboelectric charging, such as combined neoalkoxyorganometallics, including combined neoalkoxy titanates and combinedneoalkoxy zirconates, hygroscopic surfactants, such as tertiary fattyamines and their quaternary ammonium salts, such as trilaurylammoniumstearate, monoacyl glycerides, such as glycerol monostearate, monoalkylphosphates, such as stearyl phosphate, sulfonamides, such asdodecylbenzenesulfonamide, conductive particles in low concentrations,typically from 4 to 60 percent by weight conductor in the polymer,metalocenes, such as bis(methyl)cyclopentadianyl cobalt and its analogs,and the like. Fillers of this type are present in any effective ordesired amount, generally from about 0.1 to about 40 percent by weight,and preferably from about 0.5 to about 10 percent by weight.

Further, the preform can be a multi-layered structure wherein each layeris of a relative thickness with respect to the other layers thatcorresponds to the desired relative thicknesses of these layers in thefinal seamless belt prepared according to the present invention. Thus,by employing a multi-layered preform, a multi-layered seamless belt canbe prepared. The resulting seamless belt will have layers with relativethicknesses in the same ratio with respect to each other as the relativethicknesses of the layers in the preform. For example, a substantiallycylindrical preform comprising an inner layer of a conductive materialsuch as polyethylene terephthalate containing, for example, about 15percent by weight of conductive carbon black and an outer layer about 5times as thick as the inner layer of an insulating material such aspolyethylene terephthalate containing no conductive fillers can beprocessed according to the present invention to result in a seamlessbelt comprising an inner conductive layer and an outer insulating layerabout 5 times as thick as the conductive layer which can be employed asa substrate in an electrophotographic imaging member, as a dielectricreceiver for an ionographic or electrographic imaging process, or thelike.

The preform can be prepared by any suitable process. For example, thepreform can be prepared by injection molding as described in, forexample, U.S. Pat. No. 3,910,743, U.S. Pat. No. 3,936,260, and U.S. Pat.No. 4,363,619, the disclosures of each of which are totally incorporatedherein by reference. Injection molding generally entails introducing themolten polymeric material into a mold of the desired shape, allowing thepolymeric material to solidify, and removing the solid product from themold. Preferably, the injection mold is seamless in nature, since it isbelieved that surface imperfections on the preform caused by theinjection mold tend to be stretched out somewhat during the expansionprocess but may not be totally eliminated. In addition, the preform canbe prepared by extrusion processes, such as those described in, forexample, U.S. Pat. No. 4,698,196, the disclosure of which is totallyincorporated herein by reference. Generally, the extrusion processentails introducing the molten polymeric material into a mold or diecomprising an annular space between an inner cylindrical surface and anouter cylindrical surface, extruding the material in tubular form fromthe annular space while preventing collapse of the tube walls while thepolymeric material is cooling and solidifying, and recovering thecooled, solidified polymeric material in tubular form. The tube can bepulled over a sizing disk coaxial with the tube as the tube exits fromthe die. Further, multilayer preforms can be prepared by coextrusion ofmultiple layers as disclosed, for example, in U.S. Pat. No. 4,233,367,the disclosure of which is totally incorporated herein by reference. Thecoextrusion process generally entails extrusion of two or moreconcentric tubes of diferent composition, followed by contacting theouter surface of the inside tube to the inner surface of the outsidetube while both tubes are still in the melt state, followed by coolingthe two-layered tube thus formed. More than two layers can be coextrudedaccording to this process. Any other suitable method for preparing apreform can also be employed. The preform need not be completelystraight or cylindrical in configuration, since the desired shape of thefinal belt is determined during the stretch blow molding step of theprocess of the present invention. Some preforms or parisons are alsocommercially available from several sources, such as Eastman Chemicals,Kingsport, TN and Owens-Illinois Inc. in the United States and Twinpack,Inc. in Canada.

Subsequently, the preform is sealed to enable introduction of a fluidunder pressure into the preform, thereby enabling expansion of thepreform when it is heated. When the preform is prepared by injectionmolding processes, it can be designed so that it has a single openinginto which fluid can be introduced. One example of a suitable preformconfiguration that can be prepared by injection molding is illustratedschematically in FIG. 1A, which illustrates a preform 1a with an opening3a into which a fluid can be introduced. The preform illustrated in FIG.1A is equipped with an opening 5. Another example of a suitable preformconfiguration that can be prepared by injection molding is illustratedschematically in FIG. 1B, which illustrates a preform 1b with an opening3b into which a fluid can be introduced. The preform illustrated in FIG.1B is equipped with a widened edge or lip 6 for fitting the preform to apreform holder. When the preform is prepared by extrusion or coextrusionprocesses or other processes that result in a cylindrical product, thecylindrical preform is sealed at each end, with one end seal having anopening to allow introduction of a fluid under pressure into thepreform. Sealing of the cylinder ends can be by any suitable means, suchas end caps attached to the cylinder by any suitable means, such asthreading, gluing, welding, or the like. Preferably, but notnecessarily, the end of the preform opposite to that in which the fluidis to be introduced is equipped with a centering means, such as a guiderod, to facilitate centering of the preform in the mold during the blowmolding step. An example of a suitable preform configuration that can beprepared by extrusion processes is illustrated in FIG. 1C. As shown inFIG. 1C, preform 1c is sealed at one end with end cap 2 having anopening 4 into which fluid can be introduced, and is sealed at other endwith end cap 7 having attached thereto a guide rod 8 for centering thepreform within the mold.

Yet another example of a suitable preform configuration is illustratedschematically in FIG. 1D. As shown in FIG. 1D, the preform 1d is a flatplate or disk. As shown in this Figure, preform 1d is a multilayeredapproximately circular disk structure. The preform illustrated in FIG.1D can comprise two or more layers, if desired, such as a layer ofelectrically conductive material and a layer of insulating dielectricmaterial to result in a two-layered article suitable, for example, foruse as an ionographic imaging member. Alternatively, preform 1d canconsist of a single layer of a polymeric material. The preformconfiguration illustrated in FIG. 1D is suitable for use in theembodiment of the present invention as illustrated in FIG. 4, whereinthe preform is first stretched mechanically in the axial direction ofthe mold and is then stretched in the radial direction by theintroduction of a fluid into the preform. The preform illustrated inFIG. 1D need not be of a diameter as large as that of the inside of themold; upon stretching mechanically in the axial direction, followed bystretching in the radial direction by introduction of fluid, a preformof diameter smaller than the inner diameter of the mold may enableproduction of an article with enhanced radial stretch. Further, ifdesired, the disk preform illustrated in FIG. 1D need not be a perfectlyuniform, flat, circular disk. For example, the disk may be equipped witha center reference depression to enable correct placement of themechanical plunger on the disk for mechanical stretching. In addition,the disk need not be perfectly flat if a non-uniform configurationimproves the uniformity of the stretched product. Further, the flatpreform need not be circular, but can be square or of any other shapedesired. Other configurations, such as a shallow saucer configuration,are also suitable.

The preform is then heated to an appropriate stretching temperature.This temperature is equal to or greater than the glass transition pointand below the melting point of the polymer from which the preform ismade. The actual temperature employed will depend on the polymerselected for the preform. For example, a polyethylene terephthalatepreform generally is heated to a stretching temperature of from about90° to about 115° C. (which is slightly above the glass transitiontemperature of 70° to 85° C. and far below the melting temperature of245° to 265° C.) and a polypropylene preform generally is heated to astretching temperature of from about 160° to about 165° C. (which isslightly below the melting temperature of 168° C. and far above theglass transition temperature of -20° C.). For uniform heating of thepreform, it may be advantageous to rotate the preform during heating.Heating can be accomplished by any suitable means, such as by placingthe preform in a forced air convection oven at the appropriatetemperature, heating the preform by infrared radiation, heating thepreform inside of the blowing mold by forced air convection or infraredradiation, or the like. Generally, the preform is heated as quickly aspossible for economic reasons and also to minimize preformcrystallization prior to the stretch blow molding stage. For example,preforms with wall thickness of about 0.060 inch can be heated in about7 to 8 minutes with forced convective heating; preforms with wallthicknesses of about 0.125 inch can be heated in about 95 to 105 secondswith infrared heating.

Subsequently, as illustrated schematically in FIGS. 2A and 2B, theheated preform 1 is placed into a blowing mold 10 having air vents 12.The blowing mold 10 generally is substantially cylindrical in shape, andhas an inside surface preferably polished to about 4 microinches R_(a)or less when the belt to be formed is intended for use as aphotoreceptor substrate. Surface quality (R_(a)) refers to the height ofsurface defects or roughness irregularities. The R_(a) is defined as theaverage value of the departures from the center line throughout aprescribed sampling length, and is determined by running a stylus alongthe surface, plotting the surface roughness, and measuring the peaks andvalleys of the plot with respect to a center line drawn through thepeaks and valleys. When the belt formed by the process is intended foruse as a document handler belt, the mold surface can be as smooth orrough as desired, and it may even be desired to roughen the mold surfaceby processes such as sandblasting or the like to produce a belt with amatte surface. The mold preferably is free of seams and substantiallyfree of other surface irregularities on its inside cylindrical surfaceto produce a belt without surface nonuniformities. Preferably, the moldis preheated to a temperature at or above the stretching temperature toreduce post stretching mold heat up time. The preform 1 is axiallycentered within the blowing mold 10. A fluid is introduced underpressure into the heated preform 1 through an opening (not shown inFIGS. 2A and 2B). Any suitable fluid pressure can be used; typicalpressures are from about 10 to about 300 pounds per square inch. Whenair is used, it may be preferable to heat the air, for example to about100° C. Any suitable fluid can be used. For economic reasons, simpleroom air is generally preferred, although other gases, such as nitrogen,carbon dioxide, or the like, and liquids, such as water, can also beemployed. FIGS. 2A and 2B illustrate schematically two differentsuitable apparatus configurations for the stretch blow molding processof the present invention. As shown in FIG. 2A, preform 1a is equippedwith an opening 5 (as illustrated in FIG. 1A) and is held in placewithin mold 10a with preform holder 14a. Air is introduced through airinlet 16a in preform holder 14a. Mold 10a is equipped with vent holes12a to allow expansion of the preform. As shown in FIG. 2B, preform 1bis equipped with a slightly widened edge or lip 6 (as illustrated inFIG. 1B) and is held in place within mold 10b with toggle clamps 14b,which clamp preform 1b tightly to the top surface of mold 10b and retaincap 15 in place over the preform. Air is introduced through air inlet16b through an opening in cap 15. Mold 10b is equipped with vent holes12b to allow expansion of the preform. FIG. 2B also shows heating coils18, which heat mold 10b, and retaining walls 19, which retain heat inthe vicinity of mold 10b.

The mold wall is generally preheated to a temperature at or above thestretching temperature. Mold wall temperature can be controlled by anysuitable means, such as by circulating a heat transfer fluid in a jacketsurrounding the mold wall, passing a heated air stream past the moldwalls, the use of electrical resistance heaters or induction heatingcoils, or the like. As the pressure in the preform rises, it expands,generally beginning with a uniform expansion until an aneurysm forms.The region of the aneurysm then expands rapidly to the natural drawdiameter, where it is stable. (See C. Bonnebat et al., Polym. Eng. Sci.,vol. 21, no. 4, p. 189, 190 (Results and Discussion) (1981) for adiscussion of natural draw diameter for PET; this discussion is alsoapplicable to other polymers at different temperatures.) Fortemperatures above a given point (for example, with PET, the temperatureis 85° C.), the tensile stress is essentially constant as a function ofdraw ratio up to a critical draw ratio λ, called the Natural Draw Ratio.Above λ the stretching force increases very rapidly with draw ratio,referred to as strain hardening. This is the principle under whichstretch blow molding occurs. For a cylindrical parison or preform,inflation starts in the central zone and propagates to both edges of thepreform until the preform is "fully blown". At this point, the NaturalAxial Draw Ratio λL is defined as the length ratio of expanded preformto the original preform, and the Natural Radial Draw Ratio λR is definedas the diameter ratio of expanded preform to the original preform. λLand λR have different values, and are functions of temperature andpolymer molecular weight. Thus, values of λL and λR can be determinedexperimentally (as in the above reference). A theoretical expression hasbeen derived in "Blowing of Oriented PET Bottles: Predictions of FreeBlown Size and Shape", L. Erwin et al., Polym. Eng. Sci., vol. 23, no.15, p. 826 (1983), the disclosure of which is totally incorporatedherein by reference. If inflation is continued beyond this stage byincreasing the pressure, deformation occurs in the entire expandedparison or preform. Thus, it is important in that the mold diameter begreater than the natural draw diameter of the preform so that thestretch occurs unimpeded. The expanded region of the aneurysm thenpropagates throughout the length of the preform. During this time, thepreform is centered axially within the mold, which is of a diametergreater than the natural draw diameter, and the expanded preform isprevented from contacting the mold during propagation of the expandedregion. When a centering means such as a guide rod is attached to theend of the preform opposite to that from which the fluid is introduced,the centering means is retracted as the preform expansion propagates tomaintain the preform centered in the mold and to prevent the expandingpreform from contacting the mold walls.

FIGS. 3A through 3D illustrate schematically the various stages of thepreform during stretch blow molding. In FIG. 3A, the preform 1 has notyet begun to stretch. In FIG. 3B, preform 1 has formed an aneurysm 20 atapproximately the center of the cylindrical preform. In FIG. 3C,aneurysm 20 has propagated to nearly the entire length of preform 1.FIG. 3D illustrates preform 1 expanded to its natural draw diameter.

During the expansion step, the previously amorphous preform is biaxiallystretched, resulting in strain crystallization and increased tensilestrength. For example, with a polyethylene terephthalate preform, thecrystallinity of the preform prior to stretch blow molding is typicallyless than about 2 percent, and subsequent to stretch blow molding istypically about 25 percent. The biaxial orientation of the polymermolecules results in significantly increased tensile strength of thebelt.

Alternatively, instead of stretching the preform both axially andradially by pressure from the fluid, the preform can be first stretchedmechanically in the axial direction by any appropriate means, such as astretching pin or the like, followed by stretching the preform radiallyby fluid pressure. Subsequently, the resulting film can be removed fromthe mold and cut to produce a belt of the desired width. As illustratedschematically in FIG. 4, preform 1 has opening 5 and is situated in mold10 and held in place with preform holder 14. Stretching means 22 extendsthrough the opening in the preform 1 along the central axis of preform 1and mold 10. As shown in FIG. 4, stretching means 22 has stretchedpreform 1 in the axial direction but no fluid has as yet been introducedunder pressure through air inlet 16 to stretch preform 1 in the radialdirection.

Instead of a bottle-type preform, a flat or approximately flat preformas illustrated in FIG. 1D can also be used in this embodiment of thepresent invention. In addition, stretching means 22 can, if desired, beequipped with a heating means, such as a source of infrared radiation,which can heat the preform prior to stretching and can also heat thestretched preform inside the mold. For this embodiment of the invention,a flat or approximately flat preform may have advantages such assimplicity and low cost for manufacturing the preform, very high surfacequality of the preform, the ability to form multilayered preformseasily, and the like.

Subsequently, while the expanded preform is still in the mold and fluidpressure is still present, the expanded preform is rapidly heated to anappropriate heat setting temperature. This heating step subsequent tothe stretch blow molding step further increases the crystallinity levelof the preform polymer and improves the dimensional stability of thestretch blow molded tube. When this subsequent heating step is notperformed, the resulting molded item exhibits greatly reduceddimensional stability compared to a molded item that is subsequentlyheated. For example, a polyethylene terephthalate tube prepared from aninjection molded preform, blow molded at a temperature of from about 90°to about 115° C., and subsequently removed from the mold with nosubsequent heat setting step is likely to collapse and shrivel whenlater heated to a temperature of above 115° C. In contrast, apolyethylene terephthalate tube prepared from an injection moldedpreform, stretch blow molded at a temperature of from about 90° to about115° C., subjected to heat setting at a temperature of about 200° C.,and subsequently removed from the mold, exhibits dimensional stabilitywhen later heated to a temperature of about 190° C. The heat settingtemperature is above the stretching temperature and below the meltingtemperature of the polymer from which the preform is made. Generally,the heat temperature is selected to be substantially (i.e., at leastabout 10° C.) above any temperature at which the belt made from theprocess will be used. For example, when the preform is of polyethyleneterephthalate, the preform is preferably heated to a temperature of fromabout 150° to about 230° C. subsequent to expansion.

Heating to the setting temperature is performed as rapidly as possibleto ensure that the resulting belt exhibits little or no hazing orclouding and maximum heat stability. Rapid heating can be accomplishedby any suitable method, such as by heating the mold with electricalresistance heater bands, induction heating, immersing the mold in a bathof hot fluid, or the like. Generally, heating is performed over a periodof 15 minutes or less to obtain belts with the most desirable mechanicaland optical properties although longer heating periods can be used ifdesired. For polyethylene terephthalate, heat setting times of less than1 minute are preferred.

After the expanded preform has been subjected to heat setting, it israpidly cooled and removed from the mold. Cooling is performed asrapidly as possible to ensure that the resulting belt exhibits little orno hazing and maximum heat stability and to minimize the process time.Rapid cooling can be accomplished by any suitable method, such as byimmersing the mold in a bath of cold fluid, passing cold fluid throughcooling coils in a cooling band surrounding the mold, forcing cold airpast the mold, or the like. Generally, cooling is performed over aperiod of 15 minutes or less to obtain belts with the most desirablemechanical and optical properties. If desired, removal from the mold canbe facilitated by any suitable means, such as by blowing air between theexpanded preform and the mold wall, by coating the mold wall with arelease agent prior to the molding step, or the like. If desired, theexpanded preform is then cut to one or more seamless belts of thedesired size by any suitable means, such as laser cutting, knifeslitting, water jet cutting, or the like.

The process of the present invention enables formation of seamless beltswith excellent tensile strength, excellent thickness tolerances, andexcellent surface uniformity. For example, seamless belts preparedaccording to the process of the present invention from polyethyleneterephthalate and polypropylene exhibit tensile strengths of from 30,000to over 40,000 pounds per square inch, thereby enabling the use ofthinner belts for a given purpose. In addition, by virtue of thethinning process inherent in the process of the present invention,improved thickness tolerances can be obtained. For example, a preformcan be prepared with a thickness of 50 mils and a thickness tolerance of±0.25 mil. By stretching this preform by a factor of 10 during theprocess of the present invention, a seamless belt can be obtained with athickness of 5 mils and a thickness tolerance of ±0.025 mil. Similarly,a preform with a thickness of 5 mils and a thickness tolerance of ±0.25mil can be stretched by a factor of 10 during the process of the presentinvention to obtain a seamless belt with a thickness of 0.5 mils and athickness tolerance of ±0.025 mil. Further, multi-layer seamless beltscan be prepared by coextruding layers of the desired materials and ofthe desired relative thicknesses by known processes to make a preform,followed by stretching the preform according to the process of thepresent invention to obtain a multi-layer seamless belt with excellentthickness tolerances for all layers, including the thinnest layers.Additionally, the surface finish of seamless belts prepared according tothe process of the present invention, including belts containing fillerssuch as carbon black, is uniform and exhibits no waviness and puckering.

In addition, seamless belts prepared according to the process of thepresent invention generally exhibit little or no hazing.

Seamless belts prepared by the process of the present invention aresuitable for use as substrates in electrophotographic imaging members.If the belt polymer contains a conductive filler, the belt can functionas a conductive substrate. Additional layers may be added to the beltsto prepare such members. When the seamless belt prepared by the processof the present invention is not conductive, a conductive layer is firstapplied to the belt by any suitable method, such as spray coating, dipcoating, sputter coating, painting, metallizing, or the like. Theadditional layers, generally applied to the conductive surface of thebelt, may comprise a blocking layer, an adhesive layer, aphotoconductive layer, a charge transport layer, or a combination ofthese layers with or without additional layers. One embodiment of thepresent innvention is directed to a process for preparing anelectrophotographic imaging member which comprises preparing a seamlessbelt by the process of the present invention as detailed herein andcoating onto the seamless belt a layer of a photogenerating material.The imaging member can then be employed in an imaging process. Anotherembodiment of the present invention is directed to an imaging processwhich comprises (1 ) preparing an imaging member by (a) preparing aseamless belt by the process of the present invention as describedherein; and (b) coating onto the seamless belt a layer of aphotogenerating material; (2) forming an electrostatic latent image onthe imaging member; (3) developing the latent image; and (4)transferring the developed image to a substrate. Optionally, thetransferred image can be permanently affixed to the substrate by anysuitable means. Imaging members formed and employed according to theprocess of the present invention can be photoconductive orphotosensitive in nature, wherein the latent image is formed by exposureto a light image, ionographic in nature, wherein the imaging member hasa dielectric surface and the image is applied with an ionographicwriting head, or by any other suitable imaging process.

Any suitable conductive material can be employed as a conductive layerfor imaging members prepared according to the present invention,including copper, brass, nickel, zinc, chromium, stainless steel,conductive plastics and rubbers, aluminum, semitransparent aluminum,steel, cadmium, silver, gold, paper rendered conductive by the inclusionof a suitable material therein or through conditioning in a humidatmosphere to ensure the presence of sufficient water content to renderthe material conductive, indium, tin, metal oxides, including tin oxideand indium tin oxide, and the like. When the imaging member is to beemployed for ionographic imaging processes, it can consist of aconductive layer and a dielectric layer. When the polymeric seamlessbelt is prepared according to the process of the present invention, theconductive layer can be applied by any method suitable for theconductive material, such as vacuum deposition, electrolytic deposition,solvent coating, sputter coating, or the like. Alternatively, amultilayer structure comprising a conductive layer and a dielectriclayer can be prepared by formulating the preform with two distinctlayers, one conductive and one dielectric, and expanding the preformaccording to the process of the present invention. The conductive layeris of an effective thickness, generally from about 5 to about 250microns, although the thickness can be outside of this range.

In a dielectric receiver for use in ionographic imaging processes, thereceiver generally comprises a conductive layer as described forelectrophotographic imaging members and a dielectric or insulativelayer. The dielectric layer is of any effective thickness, typicallyfrom about 0.0005 inch to about 0.01 inch, although the thickness can beoutside of this range.

Any suitable blocking layer or layers may optionally be applied as oneof the imaging member coatings of this invention. Typical blockinglayers include gelatin (e.g. Gelatin 225, available from Knox GelatineInc.), and Carboset 515 (B.F. Goodrich Chemical Company) dissolved inwater and methanol, polyvinyl alcohol, polyamides, gamma-aminopropyltriethoxysilane, and the like, used alone or in mixtures and blends.Blocking layers generally range in thickness of from about 0.01 micronto about 2 microns, and preferably have a thickness of from about 0.1micron to about 1 micron. Thicknesses outside these ranges may beselected provided that the objectives of the present invention areachieved. The blocking layer may be applied with any suitable liquidcarrier. Typical liquid carriers include water, methanol, isopropylalcohol, ketones, esters, hydrocarbons, and the like.

Any suitable adhesive layer may be applied as one of the imaging membercoatings of this invention. Typical adhesive layers include polyesterssuch as du Pont 49,000, available from E.I. du Pont de Nemours &Company, poly(2-vinylpyridine), poly(4-vinylpyridine), and the like.Adhesive layers generally range in thickness of from about 0.05 micronto about 2 microns, and preferably have a thickness of from about 0.1micron to about 1 micron. Thicknesses outside these ranges may beselected provided that the objectives of the present invention areachieved. The adhesive layer may be applied with a suitable liquidcarrier. Typical liquid carriers include methylene chloride, methanol,isopropyl alcohol, ketones, esters, hydrocarbons, and the like.

Any suitable photoconductive layer or layers may be applied as one ofthe imaging member coatings of this invention. The photoconductive layeror layers may contain inorganic or organic photoconductive materials.Typical inorganic photoconductive materials include well known materialssuch as amorphous selenium, trigonal selenium, selenium alloys,halogen-doped selenium alloys such as selenium-tellurium,selenium-tellurium-arsenic, selenium-arsenic, and the like, cadmiumsulfoselenide, cadmium selenide, cadmium sulfide, zinc oxide, titaniumdioxide and the like. Inorganic photoconductive materials are normallydispersed in a film forming polymer binder. Examples of suitable bindersinclude poly(N-vinylcarbazole), polyvinylbutyral, polystyrene, phenoxyresins, polycarbonate, polyethylene terephthalate, polyN-vinylpyrrolidinone, polyvinyl alcohol, and the like. Typical organicphotoconductors include phthalocyanines, quinacridones, pyrazolones,polyvinylcarbazole-2,4,7-trinitrofluorenone, anthracene and the like.Many organic photoconductor materials may also be used as particlesdispersed in a resin binder. Typically, the photoconductive material ispresent in an amount of from about 5 to about 80 percent by weight andthe binder is present in an amount of from abut 20 to about 95 percentby weight.

Any suitable multilayer photoconductors may also be employed in theimaging member of this invention. The multilayer photoconductorscomprise at least two electrically operative layers, a photogeneratingor charge generating layer and a charge transport layer. The chargegenerating layer and charge transport layer as well as the other layersmay be applied in any suitable order to produce either positive ornegative charging photoreceptors. For example, the charge generatinglayer may be applied prior to the charge transport layer as illustratedin U.S. Pat. No. 4,265,990 or the charge transport layer may be appliedprior to the charge generating layer as illustrated in U.S. Pat. No.4,346,158, the entire disclosures of these patents being incorporatedherein by reference.

The photogenerating layer may comprise single or multiple layerscomprising inorganic or organic compositions and the like. One exampleof a generator layer is described in U.S. Pat. No. 3,121,006, whereinfinely divided particles of a photoconductive inorganic compound aredispersed in an electrically insulating organic resin binder. Usefulbinder materials disclosed therein include those which are incapable oftransporting for any significant distance injected charge carriersgenerated by the photoconductive particles. Thus, the photoconductiveparticles must be in substantially contiguous particle to particlecontact throughout the layer for the purpose of permitting chargedissipation required for cyclic operation. Thus, about 50 percent byvolume of photoconductive particles is usually necessary in order toobtain sufficient photoconductive particle to particle contact for rapiddischarge.

Examples of photogenerating layers include trigonal selenium, alloys ofselenium with elements such as tellurium, arsenic, and the like,amorphous silicon, various phthalocyanine pigments such as the X-form ofmetal free phthalocyanine described in U.S. Pat. No. 3,357,989, metalphthalocyanines such as copper phthalocyanine, quinacridones availablefrom DuPont under the tradename Monastral Red, Monastral Violet andMonastral Red Y, substituted 2,4-diamino-triazines disclosed in U.S.Pat. No. 3,442,781, polynuclear aromatic quinones, Indofast Violet LakeB, Indofast Brilliant Scarlet and Indofast Orange. Examples ofphotosensitive members having at least two electrically operative layersinclude the charge generator layer and diamine containing transportlayer members disclosed in U.S. Pat. No. 4,265,990, U.S. Pat. No.4,233,384, U.S. Pat. No. 4,306,008 and U.S. Pat. No. 4,299,897; dyestuffgenerator layer and oxadiazole, pyrazalone, imidazole, bromopyrene,nitrofluourene and nitronaphthalimide derivative containing chargetransport layers members disclosed in U.S. Pat. No. 3,895,944; generatorlayer and hydrazone containing charge transport layers members disclosedin U.S. Pat. No. 4,150,987; generator layer and a tri-aryl pyrazolinecompound containing charge transport layer members disclosed in U.S.Pat. No. 3,837,851; and the like. The disclosures of these patents areincorporated herein in their entirety.

Photogenerating layers containing photoconductive compositions and/orpigments and the resinous binder material generally ranges in thicknessof from about 0.1 micron to about 5.0 microns, and preferably have athickness of from about 0.3 micron to about 1 micron. Thicknessesoutside these ranges may be selected provided the objectives of thepresent invention are achieved. The photogenerating composition orpigment may be present in the film forming polymer binder compositionsin various amounts. For example, from about 10 percent by volume toabout 60 percent by volume of the photogenerating pigment may bedispersed in about 40 percent by volume to about 90 percent by volume ofthe film forming polymer binder composition, and preferably from about20 percent by volume to about 30 percent by volume of thephotogenerating pigment may be dispersed in about 70 percent by volumeto about 80 percent by volume of the film forming polymer bindercomposition. The particle size of the photoconductive compositionsand/or pigments should be less than the thickness of the depositedsolidified layer and, more preferably between about 0.01 micron andabout 0.5 micron to facilitate better coating uniformity.

Any suitable transport layer may be applied as one of the imaging membercoatings of this invention to form a multilayered photoconductor. Thetransport layer may contain a film forming polymer binder and a chargetransport material. A preferred multilayered photoconductor comprises acharge generation layer comprising a layer of photoconductive materialand a contiguous charge transport layer of a polycarbonate resinmaterial having a molecular weight of from about 20,000 to about 120,000having dispersed therein from about 25 to about 75 percent by weight ofone or more compounds having the general formula: ##STR1## wherein R₁and R₂ are an aromatic group selected from the group consisting of asubstituted or unsubstituted phenyl group, naphthyl group, andpolyphenyl group, R₃ is selected from the group consisting of asubstituted or unsubstituted biphenyl group, diphenyl ether group, alkylgroup having from 1 to 18 carbon atoms, and cycloaliphatic group havingfrom 3 to 12 carbon atoms and X is selected from the group consisting ofan alkyl group having from 1 to about 4 carbon atoms and chlorine, thephotoconductive layer exhibiting the capability of photogeneration ofholes and injection of the holes and the charge transport layer beingsubstantially non-absorbing in the spectral region at which thephotoconductive layer generates and injects photogenerated holes butbeing capable of supporting the injection of photogenerated holes fromthe photoconductive layer and transporting the holes through the chargetransport layer. Examples of charge transporting aromatic aminesincluding those represented by the structural formula above and othersfor charge transport layers capable of supporting the injection ofphotogenerated holes of a charge generating layer and transporting theholes through the charge transport layer includeN,N'-bis(alkylphenyl)-[1,1'-biphenyl]-4,4'-diamine wherein the alkyl is,for example, methyl, ethyl, propyl, n-butyl, etc.,N,N'-diphenyl-N,N'-bis(chlorophenyl)-[1,1'-biphenyl]-4,4'-diamine,N,N'-diphenyl-N,N'-bis(3"-methylphenyl)-(1,1'-biphenyl)-4,4'-diamine,and the like dispersed in an inactive resin binder. Examples of some ofthese transport materials are described, for example in U.S. Pat. No.4,265,990 to Stolka et al., the entire disclosure thereof beingincorporated herein by reference. Other examples of charge transportlayers capable of supporting the injection of photogenerated holes of acharge generating layer and transporting the holes through the chargetransport layer include triphenylmethane,bis(4-diethylamine-2-methylphenyl) phenylmethane;4',4"-bis(diethylamino)-2',2"-dimethyltriphenyl methane and the likedispersed in an inactive resin binder. Numerous inactive resin materialsmay be employed in the charge transport layer including those described,for example, in U.S. Pat. No. 3,121,006, the entire disclosure of whichis incorporated herein by reference. The resinous binder for the chargetransport layer may be identical to the resinous binder materialemployed in the charge generating layer. Typical organic resinousbinders include thermoplastic and thermosetting resins such aspolycarbonates, polyesters, polyamides, polyurethanes, polystyrenes,polyarylethers, polyarylsulfones, polybutadienes, polysulfones,polyethersulfones, polyethylenes, polypropylenes, polyimides,polymethylpentenes, polyphenylene sulfides, polyvinyl acetate,polysiloxanes, polyacrylates, polyvinyl acetals, polyamides, polyimides,amino resins, phenylene oxide resins, terephthalic acid resins, epoxyresins, phenolic resins, polystyrene and acrylonitrile copolymers,polyvinylchloride, vinylchloride and vinyl acetate copolymers, acrylatecopolymers, alkyd resins, cellulosic film formers, poly(amide-imide),styrene-butadiene copolymers, vinylidenechloride-vinylchloridecopolymers, vinylacetate-vinylidenechloride copolymers, styrene-alkydresins, and the like. These polymers may be block, random, oralternating copolymers.

Generally, the thickness of the solidified transport layer is betweenabout 5 to about 100 microns, but thicknesses outside this range canalso be used. The charge transport layer should be an insulator to theextent that the electrostatic charge placed on the charge transportlayer is not conducted in the absence of illumination at a ratesufficient to prevent formation and retention of an electrostatic latentimage thereon. In general, the ratio of the thickness of the solidifiedcharge transport layer to the charge generator layer is preferablymaintained from about 2:1 to 200:1 and in some instances as great as400:1.

The charge blocking layer generally has a thickness of from about 0.05to about 5 microns. The charge blocking layer prevents charge injectionfrom the conductive layer into the photogeneration layer and alsotransfers the discharged electrons into the conductive layer.

Generally, the adhesive layer is situated between the generator layerand the blocking layer, and has a thickness of from about 0.01 to about2 microns. The adhesive layer may be selected from several knownadhesives, such as PE-100, PE200, and 49000 available from Du PontChemical Company, or 4-polyvinylpyridine.

If desired, the photoreceptor may also include an overcoating. Anysuitable overcoating may be utilized in the fabrication of thephotoreceptor of this invention. Typical overcoatings include siliconeovercoatings described, for example, in U.S. Pat. No. 4,565,760,polyamide overcoatings such as Elvamide, available from E.I. du Pont deNemours & Company, tin oxide particles dispersed in a binder described,for example, in U.S. Pat. No. 4,426,435, metallocene compounds in abinder described, for example, in U.S. Pat. No. 4,315,980, antimony-tinparticles in a binder, charge transport molecules in a continuous binderphase with charge injection particles described in U.S. Pat. No.4,515,882, polyurethane overcoatings, and the like. The disclosures ofU.S. Pat. No. 4,565,760, U.S. Pat. No. 4,426,435, U.S. Pat. No.4,315,980, and U.S. Pat. No. 4,515,882 are totally incorporated hereinby reference. The choice of overcoating materials would depend upon thespecific photoreceptor prepared and the protective quality andelectrical performance desired. Generally, any overcoatings applied havea thickness between about 0.5 micron and about 10 microns.

Any of the coating materials comprising film forming polymers may bedeposited on the imaging member from solutions, dispersions, emulsionsor powders by any suitable technique. However, the deposited coatingshould form a thin substantially uniform fluid coating on the mandrelprior to solidification of the coating. Typical techniques fordepositing coatings include spray coating, dip coating, wire wound rodcoating, powder coating, electrostatic spraying, sonic spraying, bladecoating, and the like. If the coating is applied by spraying, sprayingmay be effected with or without the aid of a gas. Spraying may beassisted by mechanical and/or electrical aids such as in electrostaticspraying. Materials and process parameters are interdependent in a spraycoating operation. Some of the process parameters include propellant gaspressure, solution flow rate, secondary gas nozzle pressure, gun tosubstrate distance, gun traversal speed and mandrel rotation rate.Materials parameters include, for example, solvent mixtures which affectdrying characteristics, the concentration of dissolved solids, thecomposition of the dissolved solids (e.g. monomer, polymer), and theconcentration of dispersed solids when dispersions or solutions areutilized. The deposited coating should be uniform, smooth, and free fromblemishes such as entrained gas bubbles and the like.

Electrophotographic imaging members prepared according to the presentinvention comprise a conductive substrate layer, which may be apolymeric belt containing a conductive filler material prepared by ablow molding process as disclosed herein or a substrate consisting of abelt prepared by the process of the present invention which has beencoated with a conductive material, and a photogenerating orphotoconductive layer. Any one or more of the other layers describedherein can also be present in the imaging member. In addition, beltsprepared according to the process of the present invention can beemployed as ionographic electroreceptors. Ionographic processes aredescribed, for example, in U.S. Pat. No. 3,564,556, U.S. Pat. No.3,611,419, U.S. Pat. No. 4,619,515, U.S. Pat. No. 4,240,084, U.S. Pat.No. 4,569,584, U.S. Pat. No. 4,463,363, U.S. Pat. No. 2,919,171, U.S.Pat. No. 4,524,371, U.S. Pat. Nos. 4,254,424, U.S. Pat. No. 4,538,163,U.S. Pat. No. 4,409,604, U.S. Pat. No. 4,408,214, U.S. Pat. No.4,365,549, U.S. Pat. No. 4,267,556, U.S. Pat. No. 4,160,257, and U.S.Pat. No. 4,155,093, the disclosures of each of which are totallyincorporated herein by reference. An ionographic electroreceptorgenerally comprises at least a conductive layer and a dielectric layer.Ionographic electroreceptors can be prepared according to the presentinvention by preparing an insulating dielectric layer by a blow moldingprocess as set forth herein, followed by coating a conductive layer ontothe dielectric layer to form the electroreceptor. Alternatively, theconductive layer can be prepared by a blow molding process as set forthherein, followed by coating an insulating dielectric layer onto theconductive layer to form the electroreceptor. Additionally, anelectroreceptor can be prepared according to the present invention byfirst preparing a two layer preform with a conductive layer and adielectric layer by any suitable process, such as coextrusion,coinjection molding, or the like, followed by subjecting the two layerpreform to the blow molding process as described herein to result in anelectroreceptor with a conductive layer and an insulating dielectriclayer.

The electroreceptor thus prepared can be employed in an ionographicimaging process. Another embodiment of the present invention is directedto an imaging process which comprises (1) preparing an imaging memberhaving a conductive layer and an insulating layer by the process of thepresent invention; (2) forming an electrostatic latent image on theimaging member by ion deposition; (3) developing the latent image; and(4) transferring the developed image to a substrate. Optionally, thetransferred image can be permanently affixed to the substrate by anysuitable means.

Any suitable dry or liquid developer containing electrostaticallyattractable marking particles can be employed to develop the latentimage in the electrophotographic and ionographic imaging processes ofthe present invention. Typical dry toners have a particle size ofbetween about 6 microns and about 20 microns. Typical liquid toners havea particle size of between about 0.1 micron and about 3 microns. Thesize of toner particles generally affects the resolution of prints. Forapplications demanding very high resolution, liquid toners are generallypreferred because their much smaller toner particle size gives betterresolution of fine half-tone dots and produce four color images withoutundue thickness in dense black areas. Conventional developmenttechniques can be utilized to deposit the toner particles on the imagingsurface of the imaging member.

Two-component developers generally comprise toner particles and carrierparticles. Typical toner particles can be of any composition suitablefor development of electrostatic latent images, such as those comprisinga resin and a colorant. Typical toner resins include polyesters,polyamides, epoxies, polyurethanes, diolefins, vinyl resins andpolymeric esterification products of a dicarboxylic acid and a diolcomprising a diphenol. Examples of vinyl monomers include styrene,p-chlorostyrene, vinyl naphthalene, unsaturated mono-olefins such asethylene, propylene, butylene, isobutylene and the like; vinyl halidessuch as vinyl chloride, vinyl bromide, vinyl fluoride, vinyl acetate,vinyl propionate, vinyl benzoate, and vinyl butyrate; vinyl esters suchas esters of monocarboxylic acids, including methyl acrylate, ethylacrylate, n-butylacrylate, isobutyl acrylate, dodecyl acrylate, n-octylacrylate, 2-chloroethyl acrylate, phenyl acrylate,methylalpha-chloroacrylate, methyl methacrylate, ethyl methacrylate,butyl methacrylate, and the like; acrylonitrile, methacrylonitrile,acrylamide, vinyl ethers, including vinyl methyl ether, vinyl isobutylether, and vinyl ethyl ether; vinyl ketones such as vinyl methyl ketone,vinyl hexyl ketone, and methyl isopropenyl ketone; N-vinyl indole andN-vinyl pyrrolidene; styrene butadienes; mixtures of these monomers; andthe like. The resins are generally present in an amount of from about 30to about 99 percent by weight of the toner composition, although theycan be present in greater or lesser amounts.

Any suitable pigments or dyes or mixture thereof can be employed in thetoner particles. Typical pigments or dyes include carbon black,nigrosine dye, aniline blue, magnetites, and mixtures thereof, withcarbon black being a preferred colorant. The pigment is preferablypresent in an amount sufficient to render the toner composition highlycolored to permit the formation of a clearly visible image on arecording member. Generally, the pigment particles are present inamounts of from about 1 percent by weight to about 20 percent by weightbased on the total weight of the toner composition; however, lesser orgreater amounts of pigment particles can be present.

Other colored toner pigments include red, green, blue, brown, magenta,cyan, and yellow particles, as well as mixtures thereof. Illustrativeexamples of suitable magenta pigments include 2,9-dimethyl-substitutedquinacridone and anthraquinone dye, identified in the Color Index as CI60710, CI Dispersed Red 15, a diazo dye identified in the Color Index asCI 26050, CI Solvent Red 19, and the like. Illustrative examples ofsuitable cyan pigments include copper tetra-4-(octadecyl sulfonamido)phthalocyanine, X-copper phthalocyanine pigment, listed in the ColorIndex as CI 74160, CI Pigment Blue, and Anthradanthrene Blue, identifiedin the Color Index as CI 69810, Special Blue X-2137, and the like.Illustrative examples of yellow pigments that can be selected includediarylide yellow 3,3-dichlorobenzidene acetoacetanilides, a monoazopigment identified in the Color Index as CI 12700, CI Solvent Yellow 16,a nitrophenyl amine sulfonamide identified in the Color Index as ForonYellow SE/GLN, CI Dispersed Yellow 33, 2,5-dimethoxy-4-sulfonanilidephenylazo-4'-chloro-2,5-dimethoxy aceto-acetanilide, Permanent YellowFGL, and the like. These color pigments are generally present in anamount of from about 15 weight percent to about 20.5 weight percentbased on the weight of the toner resin particles, although lesser orgreater amounts can be present.

When the pigment particles are magnetites, which comprise a mixture ofiron oxides (Fe₃ O₄) such as those commercially available as MapicoBlack, these pigments are present in the toner composition in an amountof from about 10 percent by weight to about 70 percent by weight, andpreferably in an amount of from about 20 percent by weight to about 50percent by weight, although they can be present in greater or lesseramounts.

The toner compositions can be prepared by any suitable method. Forexample, the components of the dry toner particles can be mixed in aball mill, to which steel beads for agitation are added in an amount ofapproximately five times the weight of the toner. The ball mill can beoperated at about 120 feet per minute for about 30 minutes, after whichtime the steel beads are removed. Dry toner particles for two-componentdevelopers generally have an average particle size between about 6micrometers and about 20 micrometers.

Any suitable external additives can also be utilized with the dry tonerparticles. The amounts of external additives are measured in terms ofpercentage by weight of the toner composition, but are not themselvesincluded when calculating the percentage composition of the toner. Forexample, a toner composition containing a resin, a pigment, and anexternal additive can comprise 80 percent by weight resin and 20 percentby weight pigment; the amount of external additive present is reportedin terms of its percent by weight of the combined resin and pigment.External additives can include any additives suitable for use inelectrostatographic toners, including straight silica, colloidal silica(e.g. Aerosil R972®, available from Degussa, Inc.), ferric oxide,unilin, polypropylene waxes, polymethylmethacrylate, zinc stearate,chromium oxide, aluminum oxide, stearic acid, polyvinylidene flouride(e.g. Kynar®, available from Pennwalt Chemicals Corporation), and thelike. External additives can be present in any suitable amount, providedthat the objectives of the present invention are achieved.

Any suitable carrier particles can be employed with the toner particles.Typical carrier particles include granular zircon, steel, nickel, ironferrites, and the like. Other typical carrier particles include nickelberry carriers as disclosed in U.S. Pat. No. 3,847,604, the entiredisclosure of which is incorporated herein by reference. These carrierscomprise nodular carrier beads of nickel characterized by surfaces ofreoccurring recesses and protrusions that provide the particles with arelatively large external area. The diameters of the carrier particlescan vary, but are generally from about 50 microns to about 1,000microns, thus allowing the particles to possess sufficient density andinertia to avoid adherence to the electrostatic images during thedevelopment process. Carrier particles can possess coated surfaces.Typical coating materials include polymers and terpolymers, including,for example, fluoropolymers such as polyvinylidene fluorides asdisclosed in U.S. Pat. No. 3,526,533, U.S. Pat. No. 3,849,186, and U.S.Pat. No. 3,942,979, the disclosures of each of which are totallyincorporated herein by reference. The toner may be present, for example,in the two-component developer in an amount equal to about 1 to about 5percent by weight of the carrier, and preferably is equal to about 3percent by weight of the carrier.

Typical dry toners are disclosed in, for example, U.S. Pat. No.2,788,288, U.S. Pat. No. 3,079,342, and U.S. Pat. No. Re. 25,136, thedisclosures of each of which are totally incorporated herein byreference. If desired, development can be effected with liquiddevelopers. Liquid developers are disclosed, for example, in U.S. Pat.No. 2,890,174 and U.S. Pat. No. 2,899,335, the disclosures of each ofwhich are totally incorporated herein by reference. Liquid developerscan comprise aqueous based or oil based inks, and include both inkscontaining a water or oil soluble dye substance and pigmented inks.Typical dye substances are Methylene Blue, commercially available fromEastman Kodak Company, Brilliant Yellow, commercially available from theHarlaco Chemical Company, potassium permanganate, ferric chloride andMethylene Violet, Rose Bengal and Quinoline Yellow, the latter threeavailable from Allied Chemical Company, and the like. Typical pigmentsare carbon black, graphite, lamp black, bone black, charcoal, titaniumdioxide, white lead, zinc oxide, zinc sulfide, iron oxide, chromiumoxide, lead chromate, zinc chromate, cadmium yellow, cadmium red, redlead, antimony dioxide, magnesium silicate, calcium carbonate, calciumsilicate, phthalocyanines, benzidines, naphthols, toluidines, and thelike. The liquid developer composition can comprise a finely dividedopaque powder, a high resistance liquid, and an ingredient to preventagglomeration. Typical high resistance liquids include such organicdielectric liquids as paraffinic hydrocarbons such as the Isopar® andNorpar® family, carbon tetrachloride, kerosene, benzene,trichloroethylene, and the like. Other liquid developer components oradditives include vinyl resins, such as carboxy vinyl polymers,polyvinylpyrrolidones, methylvinylether maleic anhydride interpolymers,polyvinyl alcohols, cellulosics such as sodium carboxy-ethylcellulose,hydroxypropylmethyl cellulose, hydroxyethyl cellulose, methyl cellulose,cellulose derivatives such as esters and ethers thereof, alkali solubleproteins, casein, gelatin, and acrylate salts such as ammoniumpolyacrylate, sodium polyacrylate, and the like.

Any suitable development technique can be utilized to deposit tonerparticles on the electrostatic latent image on the imaging membersurface. Well known development techniques include magnetic brushdevelopment, cascade development, powder cloud development,electrophoretic development, and the like. Magnetic brush development ismore fully described, for example, in U.S. Pat. No. 2,791,949, thedisclosure of which is totally incorporated herein by reference, cascadedevelopment is more fully described, for example, in U.S. Pat. No.2,618,551 and U.S. Pat. No. 2,618,552, the disclosures of each of whichare totally incorporated herein by reference, powder cloud developmentis more fully described, for example, in U.S. Pat. No. 2,725,305, U.S.Pat. No. 2,918,910, and U.S. Pat. No. 3,015,305, the disclosures of eachof which are totally incorporated herein by reference, and liquiddevelopment is more fully described, for example, in U.S. Pat. No.3,084,043, the disclosure of which is totally incorporated herein byreference.

The deposited toner image is subsequently transferred to a substrate,such as paper, transparency material, or the like. Transfer can beenhanced by applying an electrostatic charge to the rear surface of thesubstrate by a charging means such as a corona device. The depositedtoner image can be transferred to a substrate such as paper ortransparency material by any suitable technique, such as coronatransfer, pressure transfer, adhesive transfer, bias roll transfer, andthe like. Typical corona transfer entails contacting the deposited tonerparticles with a sheet of paper and applying an electrostatic charge onthe side of the sheet opposite to the toner particles. A single wirecorotron having applied thereto a potential of between about 5000 andabout 8000 volts provides satisfactory transfer. After transfer, thetransferred toner image can be fixed to the receiving sheet. Typicalwell known fusing techniques include heated roll fusing, flash fusing,oven fusing, cold pressure fusing, laminating, adhesive spray fixing,and the like.

Specific embodiments of the invention will now be described in detail.These examples are intended to be illustrative, and the invention is notlimited to the materials, conditions, or process parameters set forth inthese embodiments. All parts and percentages are by weight unlessotherwise indicated.

EXAMPLE I

A cylindrical preform of the form illustrated in FIG. 1A of polyethyleneterephthalate (Eastman Kodak 7352 PET, M_(n) =24,000, M_(w) =48,000)having dimensions of 1.15 inches diameter, 5.0 inches length (excludingthe threaded section; also excluding the dome section at the tip of thepreform, the preform had a length of 4.45 inches), and 0.150 inch wallthickness having one sealed end was obtained from Eastman Chemicals,Kingsport, Tenn. The preform was axially centered in a one piececylindrical mold 12 inches long and 4.3 inches in inside diameter of6061 aluminum with an inner surface machined to a surface finish R_(a)of 18 microinches. A preliminary experiment with an identical preformwhich entailed stretch blowing the preform without a mold indicated thatthe diameter stretch ratio was 3.7 to 1 and the axial stretch ratio was2.6 to 1. Accordingly, the mold was selected to be slightly larger,i.e., using a diameter stretch ratio of 3.74 to 1 and an axial stretchratio of 2.67 to 1; thus, the mold had inside dimensions of 4.3 inchesin diameter and 12 inches in length. To seal the open end of the preformduring air pressurization, the preform was mounted on a preform holderwhich in turn was attached to the mold. While in the mold, the preformwas heated to a temperature of 100° C. by placing the mold, the preform,and the preform holder in a forced air convection oven. Subsequently,air was introduced into the preform through a high pressure air line viaquickrelease coupling at a pressure of 75 pounds per square inch tostretch the preform until it conformed to the inside of the cylindricalmold. The preform expansion proceeded with initial development of ananeurysm, which propagated through the length of the preform, followedby expansion until the preform contacted the inside mold surface. Theexpanded preform was then lowered to 40 pounds per square inch pressurein the mold and the mold, the preform, and the preform holder wereplaced into a forced air convection oven and heated to 220° C. for aperiod of 45 minutes to heat set the polyethylene terephthalate.Pressure was reduced in the preform prior to heat setting to compensatefor air pressure buildup during heating. Thereafter, the mold, preform,and preform holder were removed from the oven and cooled in tap water,and the pressurized air was released from the expanded preform. Thepreform was then removed from the mold. The resulting expanded and heatset preform had a wall thickness of 0.012 to 0.013 inch and exhibitedexcellent clarity and surface uniformity and smoothness. Subsequently,the expanded and set preform was heated to a temperature of 190° C. in aforced air convection oven for a period of 15 minutes, during which timethe preform retained its structural integrity in that it did not deform.For comparative purposes, a preform identical to the one used to makethe first expanded preform was stretch blow molded by the processdescribed above in this example, but was not subjected to the heatsetting step. Upon being placed in a forced air convection oven, thissecond non-heat set preform collapsed and shrivelled immediately.

The expanded and heat set preform exhibited an ultimate tensile strengthof 32,000 pounds per square inch in the circumferential direction.

EXAMPLE II

A cylindrical preform of the form illustrated in FIG. 1B of polyethyleneterephthalate having dimensions of 3.42 inches diameter, 8.59 incheslength, and 0.050 inch wall thickness having one sealed end was producedby an injection molding process using ICI Melinar N-5630 PET resin(intrinsic viscosity=0.63). The desired dimensions of the preform werebased on the desired dimensions of the belt to be produced from theexpanded preform, namely 42.00 inches in circumference or 13.37 inchesin diameter, 14.37 inches wide, 0.004 inch thick. The required preformoutside diameter was calculated using the equation

    OD.sub.belt =(ID.sub.preform +0.5t.sub.preform)×DSR

wherein OD_(belt) is the outside diameter of the belt to be formed,ID_(preform) is the preform inside diameter, t_(preform) is the preformwall thickness, and DSR is the diameter stretch ratio. A diameterstretch ratio of 4.0 was chosen, based on the recommendation of the PETmanufacturer of a DSR of 3.8 or more. The preform thus had an outsidediameter of 3.42 inches, a length of 6.69 inches (not including the domeportion-based on an axial stretch ratio of 3.0, calculated by 14.37[desired belt width]÷3[axial stretch ratio]=4.79 inches, with 1.9additional inches added to account for end effects and trimming), and athickness of 0.050 inch (determined from the desired final beltthickness multiplied by the two stretch ratios, i.e.,0.004×4.0×3.0=0.048). The preform was placed on a preform holder andheated to a temperature of 90° C. in a forced air convection oven for 7minutes, followed by quickly removing the preform and preform holderfrom the oven and placing them in a one piece cylindrical mold 16.0inches long and 13.414 inches in inside diameter (slightly larger thanthe desired finished belt diameter to account for thermal contraction ofthe belt during cooling). The mold was fabricated from 1025 mild steeland the inside surface was machined (lathe turned) to a surface finishR_(a) of 18 microinches. Four toggle clamps were closed onto the preformholder and the high pressure air supply hose was connected to the airinlet pipe on the preform holder via a quick-release coupling. Air wasthen introduced into the preform at a pressure of 30 pounds per squareinch to stretch the preform until it conformed to the inside of thecylindrical mold. The expanded preform was then maintained under 30pounds per square inch pressure in the mold and the mold was heated to150° C. with 3 kW silicone rubber band heaters mounted on the outer moldsurface to heat set the polyethylene terephthalate. The temperature of150° C. was the maximum temperature that could be achieved with theseheaters within a reasonable period of time (i.e., 30 minutes or less).Once 150° C. was reached, the power to the heaters was turned off andthe mold was allowed to cool by ambient cooling. The temperature of themold and expanded preform dropped to about 60° C. in about 45 minutes,at which time the mold lid was removed and the expanded preform wasremoved from the mold and trimmed. The resulting heat set belt had acircumference of 42.025 inches and an average wall thickness of 0.0035inch (actual wall thickness ranging from 0.0027 to 0.0042 inch,attributable to nonuniform preform wall thickness) and exhibited slighthazing or milkiness. The belt surface showed imperfections of the insidemold surface as well as dust particles caught between the expandedpreform and the mold wall. The heat set belt exhibited an ultimatetensile strength of 29,000 pounds per square inch in the circumferentialdirection.

EXAMPLE III

A cylindrical preform of the form illustrated in FIG. 1B of polyethyleneterephthalate having dimensions of 3.42 inches diameter, 8.59 incheslength, and 0.060 inch average wall thickness having one sealed end wasproduced by an injection molding process using ICI Melinar N-5630 PETresin (intrinsic viscosity=0.63). The preform was of the same dimensionsas that of Example II with the exception that the wall thickness wasincreased from 0.050 to 0.060 inch to result in a thicker belt. Thepreform was placed on a preform holder and heated to a temperature of90° C. in a forced air convection oven for 8 minutes, followed byquickly removing the preform and preform holder from the oven andplacing them into a one piece cylindrical mold 19.50 inches long and13.402 inches in inside diameter (already heated to 140° C.). The moldwas fabricated from case-hardened 1025 mild steel and the inner surfacewas ground to a surface finish R_(a) of 12 microinches and chromeplated. The mold was heated to 140° C. so that the time to raise themold temperature during the heat setting step could be shortened. Fourhold-down toggle clamps were used to clamp the preform holder andpreform into position on the mold apparatus. A high pressure air supplyhose was connected to the air inlet pipe on the preform holder via aquick release coupling. Air was introduced into the preform at apressure of 37 pounds per square inch to stretch the preform until itconformed to the inside of the cylindrical mold. The expanded preformwas then maintained under 37 pounds per square inch pressure in the moldand the mold was heated to 170° C. over a period of 15 minutes to heatset the polyethylene terephthalate. The steel mold was heated with 14 kWcast aluminum heater bands mounted on the outer mold surface. Once the170° C. temperature was reached, the power to the heaters was turned offand the mold was cooled by passing water through cooling coils in theheater bands. The temperature of the mold and expanded preform droppedto about 75° C. over a period of about 10 minutes, after which the moldlid was removed and the expanded preform was removed from the mold andtrimmed. The resulting heat set belt had a circumference of 41.94 inchesand an average wall thickness of 0.0045 inch (actual thickness rangingfrom 0.0036 to 0.0050 inch as a result of nonuniform preform wallthickness) and exhibited excellent clarity. The belt surface showed theimperfections of the inside mold surface as well as dust particlescaught between the expanded preform and the mold wall.

EXAMPLE IV

A cylindrical preform of the form illustrated in FIG. 1B of polyethyleneterephthalate containing 18 percent by weight of a barium sulfate fillerand having dimensions of 3.42 inches diameter, 8.59 inches length, and0.115 inch average wall thickness and having one sealed end was producedby an injection molding process using ICI Melinar B-79 PET resin. Thepreform was similar in dimension to the preform of Example II with theexception that the preform wall was increased to 0.115 inch to result ina belt with a thickness of 0.008 inch. The preform was placed on apreform holder and heated to a temperature of 90° C. in a forced airconvection oven for 15 minutes. After the preform was heated to 90° C.,it was quickly removed from the oven with the preform holder and placedinto a one piece cylindrical mold 19.50 inches long and 13.262 inches ininside diameter (already heated to 140° C.). The mold was fabricatedfrom 1025 mild steel and the inside surface was machined (lathe turned)to a surface finish R_(a) of 18 microinches. The mold was heated to 140°C. so that the time to raise the mold temperature during the heatsetting step could be shortened. Four hold down toggle clamps were usedto clamp the preform holder and preform into position on the moldapparatus. A high pressure air supply hose was connected to the airinlet pipe on the preform holder via a quick release coupling. Air wasintroduced into the preform at a pressure of 37 pounds per square inchto stretch the preform until it conformed to the inside of thecylindrical mold. The expanded preform was then maintained under 37pounds per square inch of pressure in the mold and the mold was heatedto 170° C. over a period of 15 minutes to heat set the polyethyleneterephthalate. The steel mold was heated with 14 kW cast aluminum heaterbands mounted on the outer mold surface. Once the 170° C. temperaturewas reached, the power to the heaters was turned off and the mold wascooled by passing water through cooling coils in the heater bands. Thetemperature of the mold and expanded preform dropped to about 75° C.over a period of about 10 minutes, after which the mold lid was removedand the expanded preform was removed from the mold and trimmed. Theresulting heat set belt was white in color and had a circumference of41.44 inches and an average wall thickness of 0.0078 inch (the actualthickness ranged from 0.0068 to 0.0084 inch as a result of nonuniformpreform wall thickness). The belt surface was very smooth and showedvirtually no imperfections. The heat set belt exhibited an ultimatetensile strength of 22,300 pounds per square inch in the circumferentialdirection.

EXAMPLE V

A cylindrical preform of the form illustrated in FIG. 1B of ICI MelinarN-5630 PET polyethylene terephthalate containing 15 percent by weight ofa conductive filler comprising carbon black and having dimensions of3.42 inches diameter, 8.59 inches length, and 0.115 inch average wallthickness and having one sealed end is produced by an injection moldingprocess. The preform is of the same dimensions as the preform of ExampleIII. The preform is placed on a preform holder and heated to atemperature of 90° C. in a forced air convection oven for 8 minutes.After the preform is heated to 90° C., it is quickly removed from theoven with the preform holder and placed into a one piece cylindricalmold 19.50 inches long and 13.402 inches in inside diameter (alreadyheated to 140° C.). The mold is fabricated from 1025 mild steel and theinside surface is ground to a surface finish R_(a) of 12 microinches andchrome plated. The mold is heated to 140° C. so that the time to raisethe mold temperature during the heat setting step can be shortened. Fourhold down toggle clamps are used to clamp the preform holder and preforminto position on the mold apparatus. A high pressure air supply hose isconnected to the air inlet pipe on the preform holder via a quickrelease coupling. Air is introduced into the preform at a pressure of 37pounds per square inch to stretch the preform until it conforms to theinside of the cylindrical mold. The expanded preform is then maintainedunder 37 pounds per square inch of pressure in the mold and the mold isheated to 170° C. over a period of 15 minutes to heat set thepolyethylene terephthalate. The steel mold is heated with 14 kW castaluminum heater bands mounted on the outer mold surface. Once the 170°C. temperature is reached, the power to the heaters is turned off andthe mold is cooled by passing water through cooling coils in the heaterbands. The temperature of the mold and expanded preform drops to about75° C., after which the mold lid is removed and the expanded preform isremoved from the mold and trimmed. The resulting heat set belt is blackin color and conductive, thus rendering it suitable as a conductivesubstrate for electrophotographic or ionographic imaging members. It isbelieved that the belt surface will be very smooth and will showvirtually no imperfections.

EXAMPLE VI

The seamless belt formed in Example III is made into a photoreceptor byfirst coating the outer surface of the belt with a layer of aluminum 150microns thick by vacuum vapor deposition. Subsequently, the conductivealuminum layer is coated with a photogenerating layer comprising an azophotogenerating pigment by the process described in Example V of U.S.Pat. No. 4,797,337, the entire disclosure of said patent being totallyincorporated herein by reference, wherein the photogenerating layer andcharge transport layer are coated onto the conductive belt. Thephotoreceptor thus formed is then incorporated into anelectrophotographic imaging test fixture and the imaging member ischarged negatively with a corotron, followed by exposure of the chargedmember to a light image to form a negatively charged latent image on themember. The image is developed with a two-component developer comprising2.5 percent by weight of a positively charged black toner prepared bymixing together 92 parts by weight of a styrene-n-butylmethacrylateresin, 6 parts by weight of Regal 330® carbon black from CabotCorporation, and 2 parts by weight of cetyl pyridinium chloride and meltblending in an extruder, followed by micronization and airclassification to obtain toner particles with an average diameter of 12microns, and 97.5 percent by weight of a carrier prepared by solutioncoating a Hoeganoes Anchor Steel core with a particle diameter range offrom about 75 to about 150 microns, available from Hoeganoes Company,with 0.4 parts by weight of a coating comprising 20 parts by weight ofVulcan carbon black, available from Cabot Corporation, homogeneouslydispersed in 80 parts by weight of a chlorotrifluoroethylene-vinylchloride copolymer, commercially available as OXY 461 from OccidentalPetroleum Company, which coating was solution coated from a methyl ethylketone solvent. The developed image is transferred to Xerox® 4024 paperand affixed thereto by a heated fuser roll.

EXAMPLE VII

The seamless belt formed in Example III is made into a dielectricreceiver suitable for ionographic imaging by first coating the innersurface of the belt with a layer of aluminum 150 microns thick by vacuumvapor deposition. The resulting belt has a conductive inner layer and adielectric outer layer. The belt thus formed is incorporated into anionographic imaging test fixture and a positively charged latent imageis generated on the outer dielectric surface of the belt with anionographic writing head. The latent image is developed with anegatively charged magenta liquid developer comprising an Isopar® Gliquid vehicle, magenta toner particles in an amount of 1.5 percent byweight of the developer comprising about 15 percent by weight ofHostaperm Pink E pigment and about 85 percent by weight of poly(2-ethylhexyl methacrylate) (Polysciences, Inc.), and OLOA 1200 in an amount ofabout 1 percent by weight of the solids content of the developer.Subsequently, the developed image is transferred to Xerox® 4024 paper.

The above process is repeated except that a negatively charged latentimage is generated on the outer dielectric layer of the belt with theionographic writing head and the latent image is developed with atwo-component developer comprising 2.5 percent by weight of a positivelycharged black toner prepared by mixing together 92 parts by weight of astyrene-n-butylmethacrylate resin, 6 parts by weight of Regal 330®carbon black from Cabot Corporation, and 2 parts by weight of cetylpyridinium chloride and melt blending in an extruder, followed bymicronization and air classification to obtain toner particles with anaverage diameter of 12 microns, and 97.5 percent by weight of a carrierprepared by solution coating a Hoeganoes Anchor Steel core with aparticle diameter range of from about 75 to about 150 microns, availablefrom Hoeganoes Company, with 0.4 parts by weight of a coating comprising20 parts by weight of Vulcan carbon black, available from CabotCorporation, homogeneously dispersed in 80 parts by weight of achlorotrifluoroethylene-vinyl chloride copolymer, commercially availableas OXY 461 from Occidental Petroleum Company, which coating was solutioncoated from a methyl ethyl ketone solvent. The developed image istransferred to Xerox® 4024 paper and affixed thereto by a heated fuserroll.

EXAMPLE VIII

The conductive belt formed in Example V is made into a dielectricreceiver suitable for ionographic imaging processes by coating the beltwith a dielectric layer 0.001 inch thick comprising polyethyleneterephthalate applied by a melt coating process. The resulting belt hasa conductive inner layer and a dielectric outer layer. The belt thusformed is incorporated into an ionographic imaging test fixture and apositively charged latent image is generated on the outer dielectricsurface of the belt with an ionographic writing head. The latent imageis developed with a negatively charged magenta liquid developercomprising an Isopar® G liquid vehicle, magenta toner particles in anamount of 1.5 percent by weight of the developer comprising about 15percent by weight of Hostaperm Pink E pigment and about 85 percent byweight of poly(2-ethyl hexyl methacrylate) (Polysciences, Inc.), andOLOA 1200 in an amount of about 1 percent by weight of the solidscontent of the developer. Subsequently, the developed image istransferred to Xerox® 4024 paper.

The above process is repeated except that a negatively charged latentimage is generated on the outer dielectric layer of the belt with theionographic writing head and the latent image is developed with atwocomponent developer comprising 2.5 percent by weight of a positivelycharged black toner prepared by mixing together 92 parts by weight of astyrene-n-butylmethacrylate resin, 6 parts by weight of Regal 330®carbon black from Cabot Corporation, and 2 parts by weight of cetylpyridinium chloride and melt blending in an extruder, followed bymicronization and air classification to obtain toner particles with anaverage diameter of 12 microns, and 97.5 percent by weight of a carrierprepared by solution coating a Hoeganoes Anchor Steel core with aparticle diameter range of from about 75 to about 150 microns, availablefrom Hoeganoes Company, with 0.4 parts by weight of a coating comprising20 parts by weight of Vulcan carbon black, available from CabotCorporation, homogeneously dispersed in 80 parts by weight of achlorotrifluoroethylene-vinyl chloride copolymer, commercially availableas OXY 461 from Occidental Petroleum Company, which coating was solutioncoated from a methyl ethyl ketone solvent. The developed image istransferred to Xerox® 4024 paper and affixed thereto by a heated fuserroll.

EXAMPLE IX

The conductive belt formed in Example V is made into a photoreceptor bycoating the belt with a photogenerating layer comprising an azophotogenerating pigment by the process described in Example V of U.S.Pat. No. 4,797,337, the entire disclosure of said patent being totallyincorporated herein by reference, wherein the photogenerating layer andcharge transport layer are coated onto the conductive belt. Thephotoreceptor thus formed is then incorporated into anelectrophotographic imaging test fixture and the imaging member ischarged negatively with a corotron, followed by exposure of the chargedmember to a light image to form a negatively charged latent image on themember. The image is developed with a two-component developer comprising2.5 percent by weight of a positively charged black toner prepared bymixing together 92 parts by weight of a styrene-n-butylmethacrylateresin, 6 parts by weight of Regal 330® carbon black from CabotCorporation, and 2 parts by weight of cetyl pyridinium chloride and meltblending in an extruder, followed by micronization and airclassification to obtain toner particles with an average diameter of 12microns, and 97.5 percent by weight of a carrier prepared by solutioncoating a Hoeganoes Anchor Steel core with a particle diameter range offrom about 75 to about 150 microns, available from Hoeganoes Company,with 0.4 parts by weight of a coating comprising 20 parts by weight ofVulcan carbon black, available from Cabot Corporation, homogeneouslydispersed in 80 parts by weight of a chlorotrifluoroethylene-vinylchloride copolymer, commercially available as OXY 461 from OccidentalPetroleum Company, which coating was solution coated from a methyl ethylketone solvent. The developed image is transferred to Xerox® 4024 paperand affixed thereto by a heated fuser roll.

EXAMPLE X

The seamless belt formed in Example IV is cut into 18 narrower beltseach about 1 inch wide. Eleven of these belts spaced at a distance of1/4 inch from each other are then incorporated into the recirculatingdocument handler of a Xerox® 5090 imaging apparatus. The documenthandler is of the type that employs vacuum to hold papers in the handleragainst the belts. Paper documents are placed in the recirculatingdocument handler and cycled through the apparatus to form copies. It isbelieved that the belts will exhibit no breakage, even after over100,000 cycles. In addition, since the belts have no seams ordiscontinuities, little or no dirt accumulates on the belts, andaccordingly the copies generated do not exhibit image defects such asdark lines. Further, the belts track well on the rollers of the documenthandler, exhibiting little or no deviation or wandering on the rollers,in contrast to seamed belts, which may be joined so as to form imperfectcylinders, resulting in wandering or deviation from the rollers when thebelt is used in a document handler.

Other embodiments and modifications of the present invention may occurto those skilled in the art subsequent to a review of the informationpresented herein; these embodiments and modifications, as well asequivalents thereof, are also included within the scope of thisinvention.

What is claimed is:
 1. A process for preparing an electrophotographicimaging member which comprises (a) providing a preform comprising apolymeric material; (b) heating the preform to an appropriate stretchingtemperature at or above the glass transition temperature of thepolymeric material and below the melting temperature of the polymericmaterial; (c) placing the heated preform into a substantiallycylindrical mold with a polished seamless inside surface; (d)introducing a fluid under pressure into the heated preform whilemaintaining the preform axially centered in the mold, thereby causingthe preform to expand without contacting the mold surface; (e)subsequently causing the preform to expand until it contacts the moldsurface; (f) heating the expanded preform to an appropriate heat settingtemperature above the stretching temperature and below the meltingtemperature of the polymeric material while maintaining fluid pressure;(g) subsequently cooling the set preform; (h) trimming the set preformto the desired dimensions, thus forming a seamless belt; (i) applying alayer of a conductive material to the seamless belt thus formed; and (j)applying a layer of a photogenerating material to the layer ofconductive material.
 2. A process according to claim 1 wherein theheated preform is caused to stretch in the axial direction withoutcontacting the mold surface by mechanical means prior to introduction ofthe fluid into the preform, and wherein the fluid causes the heatedpreform to stretch in the radial direction.
 3. A process according toclaim 2 wherein the preform is substantially flat prior to heating.
 4. Aprocess according to claim 1 wherein introduction of the fluid into thepreform causes the heated preform to stretch in both the axial andradial directions.
 5. A process according to claim 1 wherein thepolymeric material is selected from the group consisting of polyethyleneterephthalate, polypropylene, polyvinyl chloride, polystyrene,polyacrylonitrile, polyacetals, polyamides, polyether ether ketone, andmixtures thereof.
 6. A process according to claim 1 wherein thepolymeric material contains a filler.
 7. A process according to claim 1wherein the polymeric material is polyethylene terephthalate and thepreform is heated to a temperature of from about 90° C. to about 115° C.prior to causing the preform to expand.
 8. A process according to claim1 wherein the polymeric material is polypropylene and the preform isheated to a temperature of from about 160° C. to about 165° C. prior tocausing the preform to expand both axially and radially withoutcontacting the mold surface.
 9. A process according to claim 1 whereinthe fluid is introduced into the heated preform at a pressure of fromabout 10 to about 300 pounds per square inch.
 10. A process according toclaim 1 wherein the polymeric material is polyethylene terephthalate andthe expanded preform is heated to a temperature of from about 150° toabout 230° C. subsequent to expansion.
 11. A process according to claim1 wherein the preform is heated to the setting temperature within aperiod of 15 minutes or less.
 12. A process according to claim 1 whereinthe preform is cooled within a period of 15 minutes or less.
 13. Aprocess for preparing an electrophotographic imaging member whichcomprises (1) preparing a biaxially stretched preform by the process ofclaim 2, wherein the preform comprises a polymeric material containing aconductive filler; (2) trimming the set preform to the desireddimensions, thus forming a seamless belt; (3) applying a layer of aconductive material to the seamless belt thus formed; and (4) applying alayer of a photogenerating material to the layer of conductive material.